1. Field of the Invention
The present invention relates to electromagnetic radiating antennas. More particularly, the present invention relates to an antenna that can provide an omnidirectional and a directional radiation pattern over at least two different frequency bands of operation.
2. Background Information
There are various dual-band and dual polarization omnidirectional antennas found in the prior art. In U.S. Pat. No. 4,814,777, “Dual-Polarization Omni-Directional Antenna System”, a dual-polarization, omnidirectional is disclosed. In U.S. Pat. No. 4,410,893, “Dual Band Collinear Dipole”, a dual-band collinear dipole antenna that provides omnidirectional patterns in two frequency bands is disclosed. The disclosure of these patents is hereby incorporated by reference in their entirety.
A Yagi-Uda dipole antenna has at least three dipole elements: a dipole reflector, a driven dipole element (feed element), and a dipole director. A Yagi-Uda dipole antenna operates at one frequency band to produce directed radiation. Yagi-Uda antennas are discussed in H. Yagi, “Beam Transmission of Ultra Short Waves,” Proc. IRE, vol. 26, June 1928, pp. 715-741; T. Milligan, Modern Antenna Design, McGraw-Hill, New York, 1985, pp. 332-345; and J. D. Kraus, Antennas, 2nd Edition, McGraw-Hill, New York, 1988, pp. 481-483, the disclosures of which are incorporated herein in their entirety.
It would be useful for an antenna to be able to simultaneously produce a directional radiation pattern over one frequency band and an omnidirectional radiation pattern over another frequency band.